There are basically three types of primary storage drives for PCs: hard disk drives, solid state drives, and the far less common "solid state hybrid drives." Solid state drives (SSDs) are often blazingly fast—letting you startup Windows or launch applications in a fraction of the time it takes when using a hard drive—but the average cost of a SSD is much higher than the price of a HDD. This is where hybrid drives really shine.
The Seagate Momentus XT has been the most popular hybrid drive available to consumers for more than a year. The new second generation Seagate Momentus XT promises to deliver faster performance and greater storage capacity at a fraction of the cost of a SSD. We took a look at the new 750GB Momentus XT ($245) to find out if this is the best storage drive for your laptop.
What is a Hybrid Drive?
Without getting too technical, a solid state hybrid drive is essentially a small amount of flash memory combined with a traditional hard disk drive. In the case of the new Seagate Momentus XT, you get 8GB of SLC NAND flash memory and a 750GB 7200rpm hard drive with 32MB of cache and a SATA 6GB/s interface.
You never actually see the 8GB of flash storage because the 750GB hard drive is the primary storage space where your data is read and written. A complex set of firmware algorithms configure blocks of commonly used data onto the 8GB of flash so it can be accessed as quickly as possible. In short, a hybrid drive gives you SSD-like speeds when accessing the data you use most. The rest of the time it works like a standard hard drive.
That said, the firmware in the new 750GB Seagate Momentus XT is constantly learning and adapting to your activities in order to "pre-cache" the most important files to the 8GB SSD inside the drive.
FAST Factor: New and Improved
The old 500GB Seagate Momentus XT was the first hybrid drive to use "Adaptive Memory" technology. This is Seagate's marketing term for the previously mentioned firmware algorithms that monitor data access, place "qualified data" in the NAND flash and organize frequently used data and little-used data in a way that minimizes the amount of time the drive spends looking for files.
Adaptive memory technology is essentially what makes a hybrid drive work, but Seagate wanted the new Momentus XT to "learn" faster than before. And so FAST Factor was born. FAST Factor is a combination of two new firmware algorithms: Seagate FAST Boot and FAST Management. FAST Boot basically sets aside a special section of the NAND flash dedicated for booting the operating system. FAST Management is more complicated, but it's a self-learning algorithm that streamlines that integration of the solid state memory and HDD.
Bottom line, the new 750GB Momentus XT offers 50 percent more storage capacity, 1.5X faster performance (thanks in part to FAST Factor), double the NAND flash and double the interface speed of the 500GB Momentus XT.
Performance and Benchmarks
If you read the first half of this review closely then you probably realized why benchmarking a hybrid drive is tricky. Since a hybrid drive uses complex firmware algorithms to learn how to be fast, you can't simply run basic synthetic benchmarks once or twice to find out the maximum read and write speeds. In fact, you have to run the same benchmarks and real-world Windows boot and application tests at least three or more times in a row in order for the Momentus XT to learn which files are most important and dedicate the appropriate amount of flash storage space.
For comparison purposes we tested the new 750GB Seagate Momentus XT against two SSDs (the Kingston HyperX 240GB and 256GB Samsung 470 Series) and two standard hard drives (the 1TB Western Digital Scorpio Blue WD10JPVT and 1TB Samsung Spinpoint M8). First, we used CrystalDiskMark to test both the sequential and random read and write speeds of all drives.
CrystalDiskMark storage drive performance test:
 750GB Seagate Momentus XT |
 Kingston HyperX 240GB |
 256GB Samsung 470 Series |
 1TB Western Digital Scorpio Blue |
 1TB Samsung Spinpoint M8 |
Next, we compared the Momentus XT against the fastest SSD we tested--the Kingston HyperX 240GB--using PCMark Vantage and PCMark 7. We also ran several timed tests of Windows 7 boot and launched Photoshop CS5 64-bit and opened a 2.7MB JPEG file. Since the firmware in the Momentus XT needs time to learn which files are important we recorded the Windows 7 boot time and Photoshop times of the drive in both a "fresh" state (first test result) and a "learned" result (recorded after running the same test four times).
PCMark Vantage HDD Test Suite:
 750GB Seagate Momentus XT |
 Kingston HyperX 240GB |
PCMark 7 System Storage Tests:
 750GB Seagate Momentus XT |
 Kingston HyperX 240GB |
Windows 7 Boot Time Comparison:
Photoshop CS5 Application Launch Comparison:
Conclusion
Should you spend $245 on the new 750GB Seagate Momentus XT when you can buy a traditional laptop hard drive with 1TB of storage capacity for slightly less? The short answer: Yes. While 1TB notebook hard drives like the Western Digital Scorpio Blue WD10JPVT and the Samsung Spinpoint M8 offer a massive amount of storage and reasonable speed, there is just no way that a traditional hard drive can match the speed of the new Momentus XT after the drive has "learned" which files you use on a regular basis.
Windows boot times are fast, application switching is snappy, and the cost per GB is far more reasonable than a high-performance SSD. The Kingston HyperX 240GB SSD is amazingly fast, but that drive costs $470 at the time of this writing. The Momentus XT is basically half the price for three times more storage space.
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